Help: unreliable smb mount to NTFS disk

I have a linux machine at work that has several smb mounts to a network
fileserver (NTFS) that up until recently has been working just fine. We
store a large number of locally accessed data files which I read and
write. But lately, and with increasing frequency, some of the
subdirectories appear empty from my linux machine, while all the files are
there in actuality and accessible as normal from windows machines. This
morning it has been sporadic. For example, I can do an 'ls' on a network
subdirectory and show no contents, then do an 'ls -a' and everything
appears, yet if I try to filter on it, say 'ls -a "*.dat" I get no
contents again, even though there are hundreds of such files and normally
this functions properly. Then it will quit showing anything no matter what
I do.

This is a real problem, rendering it impossible for me to do work on the
linux machine. Has anyone run into anthing like this? Is the a fix?

Thanks.

-Jeff